Combustion apparatus



April 21, 1959 G. E. POWELL 2,

COMBUSTION APPARATUS I Filed Feb. 11, 1955 2 Sheets-Sheet 1 INVENTOR GERALD E. P W

WM &/ BY YMMV ATTORN EY S April 1959 G. E. POWELL 2,882,843

COMBUSTION APPARATUS Fil ed Feb. 11, 1955 2 Sheets-Sheet 2 INVENTQR GERALD E PowELL COMBUSTION APPARATUS Application February 11, 1955, Serial No. 487,631

Claims priority, application Great Britain February 24, 1954 4 Claims. (Cl. 110-28) This invention relates to combustion apparatus for burning liquid, gaseous or powdered fuel and of the kind comprising a chamber into which the fuel is delivered one end of which is connected to an air delivery passage for the combustion air, while the other end is connected to an outlet passage for the escape of the products of combustion, and has for an object to provide improved combustion apparatus of the above kind in which efiicient combustion of the fuel will tend to be attained.

Combustion apparatus for the burning of liquid, gaseous or powdered fuel according to the present invention comprises a tubular chamber, an air delivery passage leading into one end of the chamber, an outlet passage for the escape of the products of combustion, with or without unburnt air, leading from the other end of the charm her, a tubular mixing passage (hereinafter for convenience called the primary mixing passage) arranged so that gases can flow therethrough from the end of the chamber adjacent to the outlet passage to the end adjacent to the air delivery passage, means for delivering fuel into the primary mixing passage, and deflecting means arranged to prevent air from the air delivery passage entering the adjacent end of the primary mixing passage and to cause such air to flow, with fuel and gas from the adjacent end of the primary mixing passage, into a passage (hereinafter termed the secondary mixing passage).

Thus the arrangement is such that a proportion of the burnt gases from the end of the chamber adjacent to the outlet passage flows continuously through the primary mixing passage so as to mix with fuel therein and emerge therefrom into the main air stream flowing into the secondary mixing passage.

In combustion apparatus according to the invention the extent to which combustion may take place respectively in the primary mixing passage, in the secondary mixing passage, and on the chamber beyond the second ary mixing passage, may vary according to the operating conditions and the dimensional characteristics of the apparatus.

The primary mixing passage preferably lies wholly within the secondary mixing passage so that the secondary mixing passage constitutes a secondary mixing zone wholly enclosing the primary mixing zone. For example the primary mixing passage may be of solid cylindrical cross section, being constituted by the space within a single tubular wall which constitutes the inner wall of a surrounding annular secondary mixing passage, or the primary mixing passage may be of annular form arranged so that it divides the secondary mixing passage into two concentric parts lying respectively within and around it.

Three forms of the invention are shown somewhat diagrammatically by way of example in the accompanying drawings, in which:

Figure 1 is a sectional side elevation of one form of combustion apparatus according to the invention, the section being taken in a plane containing the axis of the combustion apparatus,

Figure 2 is a similar view to Figure 1 of an alternative nited f ftfiS Patent 0 2,882,843 Patented Apr. 21, .1959

form of combustion apparatus according to the invention,

Figure 3 is a similar view to Figure 1 of a still further form of combustion apparatus according to the invention, and

Figure 4 is an end elevation of the construction shown in Figure 3 viewed from the right in Figure 3.

In the construction shown in Figure l the apparatus comprises a tubular chamber consisting of two approximately cylindrical portions A and A arranged end to end and joined by a frustoconical intermediate portion A the portion A being of larger diameter than the portion A. The end of the portion A remote from the portion A is connected as shown to a compressed air delivery passage B to which air under pressure is delivered in some well known manner, while the end of the portion A which for the sake of convenience has not been shown, will be connected to an outlet passage by which the products of combustion, with any unburnt air, from the apparatus will be delivered to the point or points of use.

Arranged so as to extend across the inlet end of the portion A of the chamber referred to is a deflector plate C which is provided adjacent to its circumference with a ring of apertures C for the passage of air from the air delivery passage B into the chamber A, A A

Supported, from the plate C by a series of brackets D is a tubular member E constituting a primary mixing passage, which it will be seen extends from a point displaced by a small distance from the inlet end of the portion A of the chamber A, A A to a point somewhat beyond the adjacent end of the portion A of this chamber, a gap B being provided between the plate C and the adjacent end of the primary mixing passage E.

Supported from the centre of the plate C is a fuel injection nozzle F by which fuel can be delivered in a wide cone of spray into the adjacent end of the primary mixing passage E as shown at F In operation the main air flow takes place from the orifices C through the annular chamber G between the wall of the chamber A, A A and the wall of the primary mixing passage E, which annular chamber constitutes the secondary mixing passage, while there will be induced by this flow a continuous'flow of gas from right to left through the primary mixing passage E and out through the gap E into the passage G, this flow carrying with it the fuel delivered by the nozzle F. This fuel may either be in a substantially unburnt, or in a partially burnt state, according to the operating conditions, and combustion will be completed in the passage G or partly in this passage and partly in the portion A of the chamber A, A A

The cross-sectional area of the combustion chamber at A is considerably greater than at A and when air is delivered under pressure through the combustion chamber, the pressure in the part A will be greater than in the part A where the air speed is higher and that therefore the gas flow through the apparatus will tend to be in the direction indicated by the arrows. Moreover, when lighting up" the mixture will be initially ignited by a glow plug or the like in the main combustion chamber, as will be obvious to anyone skilled in this art.

It will thus be apparent that the gases which flow continuously from right to left in the primary mixing passage E will be composed partially of products of combustion and will thus be in a highly heated state.

While the dimensions of combustion apparatus according to the invention may vary widely, in one example of the form of the invention shown in Figure l the cross sectional area of the primary mixing chamber E may be about 1.35 sq. in. the cross sectional area of the secondary mixing chamber G may be about 1.9 sq. in. and

the diameter of the portion A of the chamber may be about 3 in.

In the alternative construction shown in Figure 2 the combustion apparatus comprises a chamber consisting of a smaller diameter part I-I and a larger diameter part H arranged end to end," the left hand end of the chamber being connected to a compressed air delivery passage 1 while the,right hand end constitutes or leads into an outlet passageleading to the point or points at which the combustion products from the apparatus are to be used.

Within the part H of the chamber is supported by brackets K a conical deflector K the circumferential edge of which is spaced from the wall of the chamber by a gap K and supported from this deflector by brackets his a tubular member L constituting a primary mixing passage. A fuel delivery nozzle M 'is arranged to deliver fuelrinto the interior of the member L Swirl-producing vanes, indicated at N may be provided in the passage J as shown to cause theair to rotate about the axis of this passage before passing through the gap K The construction shown in Figure 2 operates in much the same way as that shown in Figure 1. Thus the main airstream flows through the gap K and the annular chamber 0 formed by the wall of the chamber J and the member L while there is a continuous flow of mixed air and products of combustion from right to left through the primary mixing passage L which mixture of air and combustion products thus mixes with the fuel delivered through the nozzle M and passes with such fuel in either a substantially wholly or a partially unburnt state into the chamber 0.

In the construction shown in Figures 3 and 4, the general arrangement resembles that shown in Figure 2, but the construction of the parts is such that the primary mixing passage is annular. Thus in the construction shown in Figures 3 and 4 the apparatus comprises a chamber having parts P and P respectively of smaller and larger diameter, an annular bafile Q corresponding to the baffle K a primary mixing chamber of annular form formed between concentric inner and outer walls R and R carried by struts R and a series of fuel in jection nozzles S. The secondary mixing passage in this case, which functions as the main combustion chamber, comprises concentric inner and outer parts T, T while swirl-producing guide vanes U may be provided in advance of the baifie Q.

The operation of this construction is similar to that of the construction shown in Figure 2 except that as will be seen the main air stream passes partly outside and partly in'side the primary mixing passage R, R

As mention ed, the extent to which the combustion takes place respectively in the primary mixing passage, the secondary mixing passageand in the chamber beyond this nozzle in apparatus according to the invention depends on the dimensional characteristics of the apparatus and the working conditions. In general it has been found,

however, that under most operating conditions some degree of combustion tends to take place in the primary mixing passage, that under low and medium load conditions combustion initiated in the primary mixing passage tends to continue throughout the secondary mixing passage into the chamber beyond it and that with increases in load the degree of combustion which takes place in the secondary mixing passage decreases until at full load, the greater proportion at least of the combustion tends to take place in the chamber beyond the end of the secondary mixing passage.

I claim:

I. Combustion apparatus for the burning of liquid, gaseous or powdered fuel comprising a main combustion chamber, an air delivery passage leading into a first end of the main combustion chamber, an exhaust passage laeding from the second end thereof, an annular primary mixing passage one end of which is in open communication with the second end of said combustion chamber and the other end of which communicates with the first end of the combustion chamber through an injector orifice causing flow from the primary mixing passage into the first end of the combustion chamber through the said orifice and causing part of the combustion products issuing from the second end of the main combustion chamber to enter the said primary mixing passage when a gas flow is induced through the combustion chamber from the first to the second ends thereof, said annular primary mixing passage dividing said combustion chamber into two concentric parts, the inner Wall of the outer part being constituted by the outer wall of the primary mixing passage while the outer wall of the inner part is formed by the inner wall of the primary mixing passage, and fuel injection means for delivering fuel into the primary mixing passage.

2. Combustion apparatus as claimed in claim 1 in which the primary mixing passage comprises inner and outer walls and an end wall, said end wall being spaced from said concentric inner and outer walls to leave a gap, said gap forming said ejector orifice.

3. Combustion apparatus as claimed in claim 2 in which said end wall is in the form of an annulus or" V-shaped cross section.

4. Combustion apparatus as defined in claim 1, in which said fuel injection means comprises a plurality of nozzles circumferentially spaced around the annular primary mixing passage.

References Cited in the file of this patent UNITED STATES PATENTS 

